Defense One : "What would ending bulk collection mean for intelligence collection? Last year, the National Academy of Sciences, or NAS , began looking at what would happen if U.S. spies no longer had easy access to phone records... The most important conclusion comes early on: a huge database of the phone records of millions of people is quite valuable to signals intelligence, or SIGINT ."
"Metadata can be defined, broadly, as all the data that you produce through your exchanges with digital devices... What does the intelligence community get from all the metadata it collects and stores? The report outlines three broad areas, starting with 'contact chaining.' Phone numbers, time logs, and other pieces of metadata can be used to find hidden connections between people: middlemen, hidden contacts, or simply mutual acquaintances."
"Next is alternate identifier discovery, aka finding digital aliases: names, usernames, and even different communications methods a person uses. Lastly, there is triage, or ranking the urgency of threats. The larger the trove of metadata on hand, and the farther an individual’s 'stream' extends backward into time, the more opportunity there is to find potentially useful information."